A conventional linear actuator for a vehicle occupant restraint system comprises a cylinder, a piston shiftable therein and consisting of a locking part including a conical outer section and a sealing part coaxial with said locking part, and further a plurality of locking bodies shiftably arranged between said conical outer section of said locking part and the inner wall of said cylinder and a pulling element connected to said piston by means of a holding part.
Such a linear actuator serves to convert the energy of a highly pressurized gas into a tensioning stroke which may be used to eliminate the slack of a seat belt system by, for example, rotating the belt reel of a belt retractor in the coiling direction or by suitably displacing the buckle of a seat belt.